Enhanced capacitance of rectangular-sectioned polypyrrole microtubes as the electrode material for supercapacitors

Abstract

Rectangular-sectioned polypyrrole microtubes (R-PPy) were synthesized in aqueous solution with β-cyclodextrin (β-CD)/I₂ inclusion compound and FeCl₃ by chemical oxidation. Field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to characterize the formation and molecular structure of R-PPy. From the results of the characterization, Complexes of β-CD/I₂–Fe²⁺ acted as the soft-template during the synthesis process of rectangular-sectioned polypyrrole microtubes. Some I⁻ ions retained in the backbone of the as-prepared PPy served as the counter ions after rinsing. Furthermore, R-PPy demonstrated higher conductivity and better electrochemical properties than PPy particles synthesized by the conventional method (C-PPy). The specific capacitance of R-PPy (322.5 F g⁻¹ at the current of 1 A g⁻¹) is almost twice as large as that of C-PPy. The original specific capacitance of R-PPy can be maintained at around 83.3% whereas it was only about 61.5% for the C-PPy after 2000 charge–discharge cycles. The larger specific capacitance and relatively high cycling stability of R-PPy make it a more attractive candidate for energy storage electrodes than C-PPy.